Alcohol creates common knowledge

Some of my friends don’t know what drinking is for, and even among those who do, they don’t all know that they all know what drinking is for. So here is my picture of what drinking is for.

The standard story is that drinking is good because it lowers people’s inhibitions. But here is an interesting observation: people like to synchronize their drinking, by clinking their glasses together and all drinking at the same time. What does this accomplish that everyone drinking independently doesn’t accomplish?

I think social drinking – specifically, rituals where everyone drinks together – is mostly not about lowering everyone’s inhibitions, it is mostly about creating common knowledge that everyone’s inhibitions have been lowered. That is, everyone’s inhibitions have been lowered, everyone knows everyone’s inhibitions have been lowered, everyone knows everyone knows everyone’s inhibitions have been lowered, and so forth.

Suppose, for example, that I want to flirt at parties, but I think I’m bad at it, and I worry I’ll be judged for doing it badly if I do it while I’m sober. So I get drunk. But wait: if people don’t know that I’m drunk, then they’ll see me flirting and think I’m sober, so they might judge me anyway. So if I really don’t want to feel like I might be judged at parties, I need to know that other people know that I’m drunk.

But actually there’s more: suppose I know that people know that I’m drunk, but other people don’t know that. Then I flirt with Alice, badly. Alice looks at me, and she sees a person who’s flirting with her badly and drunk, but who doesn’t know whether or not Alice knows he’s drunk. So she might judge me as the sort of person who flirts with girls badly even when they don’t know that he’s drunk. Or at least, I might imagine all this, and worry about being judged as not having the social skill of telling when it’s acceptable to flirt badly (which is a different thing from being judged as bad at flirting). To avoid this, I need to know that other people know that I know that they know that I’m drunk.

But still there is more: suppose I know that people know that I know that people know that I’m drunk, but other people don’t know that. Then I flirt with Alice’s friend Brenda, badly. Alice looks at me while thinking about Brenda. She sees a person who’s flirting with Brenda badly and drunk, such that Alice knows he’s drunk, but such that Alice doesn’t know whether Brenda knows he’s drunk. So she might judge me, on Brenda’s behalf, as the sort of person who flirts with a girl badly even when other people don’t know whether the girl knows that he’s drunk. Or at least, I might imagine all this, and worry. To avoid this, I need to know that other people know that I know that they know that I know that they know that I’m drunk. (Phew.)

And so forth. How could I ever come to know all this?

Suppose we all face each other, publicly drink in front of each other, then all publicly say “Cheers!” at the same time.

We’re all about to get drunk.

We’ve all seen each other drink, so we all know that we’re all about to get drunk.

We’ve all seen and heard each other drink and say “Cheers,” so we all know that we all know that we’re all about to get drunk.

We’ve all seen each other see and hear each other drink (this is why we should be facing each other, so that it’s common knowledge that everyone’s attention is on this thing that we’re doing) and say “Cheers,” so we all know that we all know that we all know that we’re all about to get drunk.

And so forth.

Now we can all flirt with each other, or whatever.

Incidentally, this post mostly isn’t about drinking; probably all social rituals work like this. Weddings create common knowledge that people are married; funerals create common knowledge that people are dead; etc. Kevin Simler, among others, has written a lot about this sort of thing.

I think past a certain point – and it’s unclear to me where that point is – the exhaustive search gets heuristically replaced by some kind of fuzzy sense of “what’s basically common knowledge.” Before that point I think there are dynamics like the one you describe, where A is thinking about B’s reaction to C’s reaction to D etc., and possibly some of A, B, C, D are the same people which makes things interesting. I picked the drunk flirting example because I wanted to match the various states of common knowledge relatively clearly to people’s existing social intuitions / emotions and I think people have relatively strong senses of what the various states are like here, but my expectation is that this sort of thing is happening in social situations basically all the time.